Solubilizers liquid cosolvents

According to the present results the marked changes of isotropic liquid regions at the PIT described by Shinoda and co-workers (29, 30, 31, 32, 33) appear limited to micellar associations and solubilization. The cosolvency of water and hydrocarbon in the emulsifier and the liquid crystalline phase region seem to undergo only small changes. 

Aromatic steroids are virtually insoluble in liquid ammonia and a cosolvent must be added to solubilize them or reduction will not occur. Ether, ethylene glycol dimethyl ether, dioxane and tetrahydrofuran have been used and, of these, tetrahydrofuran is the preferred solvent. Although dioxane is often a better solvent for steroids at room temperature, it freezes at 12° and its solvent effectiveness in ammonia is diminished. Tetrahydrofuran is infinitely miscible with liquid ammonia, but the addition of lithium to a 1 1 mixture causes the separation of two liquid phases, one blue and one colorless, together with the separation of a lithium-ammonia bronze phase. Thus tetrahydrofuran and lithium depress the solubilities of each other in ammonia. A tetrahydrofuran-ammonia mixture containing much over 50 % of tetrahydrofuran does not become blue when lithium is added. In general, a 1 1 ratio of ammonia to organic solvents represents a reasonable compromise between maximum solubility of steroid and dissolution of the metal with ionization. 

For oral liquids, taste masking becomes essential. The effects of solubilizing agents such as complexing agents and cosolvents on taste need to be evaluated. 

Often a cosolvent is used in order to solubilize particularly polar substrates such as sugars and amino acids. Surfactants or additional solvents may also allow adequate solvation of enzymes. In some cases two-phase systems can be used to conduct bioconversion. For example, Reetz and coworkers employed both SCFs and ionic liquids in a semi-continuous... 

Liquid solubilizers act by reducing the dielectric constant properties of the solvent system, thereby reducing the electrical conductance capabilities of the solvent and increasing the solubility of hydrophobic or non-polar drugs. Lanoxin, Valium, and Nembutal are examples of commercially available sterile solutions containing cosolvent solubilizers. A popular combination consists of 40% propylene glycol and 10 /o ethanol in water. 

A very special type of cosolvent is a surfactant. Recently, DeSimone and coworkers have developed surfactants that can solubilize polymeric substances in supercritical carbon dioxide (see Johnston, these proceedings). Amongst many applications visualized by this group, the substitution of liquid carbon dioxide for CFCs in dry cleaning operations features prominently. 

Phase behavior experiments should be performed to identify surfactants with high contaminant solubilization, fast coalescence rates to classical microemulsions and minimal liquid crystal/gel/ macroemulsion forming tendencies over the expected range of conditions of temperature, electrolyte, surfactant, cosolvent and contaminant concentrations. The viscosity of both the aqueous surfactant solution that is injected and the microemulsion that forms when it mixes with and solubilizes the NAPL should be low, i.e. not much greater than the corresponding water (or polymer solution if polymer is added to the water). 

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